Not Applicable
Not Applicable
1. Field of the Invention
The present invention is in the field of tools used to retrieve lodged or stuck items, called fish, from a well bore or casing.
2. Background Art
In the art of well drilling and workover, it is common to have a need to retrieve a stuck tool or other item from the well bore or casing. For the purposes of describing the invention herein, the terms casing and bore hole should be understood to mean any well bore, casing, or other tubing within which items may be lodged or stuck. Stuck items are commonly called fish. The fish may be a broken tool which has inadvertently stuck in the casing, or it may be a tool such as a whipstock, which is intentionally installed in the casing, to be removed or fished out later. Some types of fish have specially designed fishing tools which are suitable for latching onto a fishing contour on the uphole end of the fish. Others may be retrievable with a more general purpose fishing tool which is designed to latch onto many different configurations of fish. One example is a latch mechanism made up of a collet and a central spear, in which the central spear assists the collet in latching onto the fish.
Regardless of whether the fish is to be retrieved with a specially designed fishing tool or with a general purpose fishing tool, it is necessary for the tool to align with the fish, to a greater or lesser degree, depending upon the particular fish and the particular fishing tool. In some cases, as the fishing tool is run into the hole, the latch mechanism may be generally aligned with the center of the casing or bore hole, and the upper end of the fish may be aligned to one side, or vice versa. Such misalignment can make it very difficult to latch onto the fish with the fishing tool.
The possibility for such misalignment is even more likely to occur when the fish lies in a highly deviated or horizontal hole. In such situations, the operator usually relies upon gravity to deflect the fishing tool toward the same side of the casing as the uphole end of the fish. However, where an inflation element or whipstock is lodged in a highly deviated bore hole or casing, the uphole end of the fish may be positioned in the center of the hole, or even near the upper side of the deviated hole. Where gravity deflects the latch mechanism of the fishing tool toward the lower side of the deviated hole, latching onto this type of fish may be impractical at best. Since the present invention addresses the alignment of fish and fishing tools in deviated holes as well as vertical holes, the terms uphole and downhole will generally be used herein, it being understood that these terms mean the same as the terms upper and lower, respectively, in a vertical hole.
The fishing tool may have bow centralizers installed to position the latch mechanism, or bent subs may be used to orient the latch mechanism properly via a trial and error type operation. These methods can be less than satisfactory, and they can consume valuable time.
The present invention provides a method and apparatus for guiding a latch mechanism and a fish into engagement, regardless of their relative positions in the bore hole or casing. The fishing tool is lowered downhole on a work string, until it is positioned just above a fish. In the running position, a plurality of guide fingers on the downhole end of the tool are retracted radially inwardly, minimizing the overall diameter of the tool. This can be accomplished with a sleeve at least partially surrounding the guide fingers, for example, contacting the outer edges or surfaces of the fingers to hold them radially inwardly. When the tool is just above the fish, a piston is hydraulically driven longitudinally, in either the uphole or downhole direction relative to the mandrel of the tool, to shift the sleeve longitudinally and expand the downhole ends of the guide fingers until the fingers contact the casing. The sleeve can have slots which contact radially extending tangs on the upper ends of the fingers to rotate the lower ends of the fingers radially outwardly.
In this expanded configuration, the guide fingers are arrayed in a basically frusto-conical array, with the base of the frusto-conical array downhole and the apex of the frusto-conical array uphole. A latch mechanism, such as a collet and spear assembly, is mounted on the fishing tool near the downhole end of the mandrel, and near the uphole ends of the guide fingers. Other types of latch mechanisms may also be used. The guide fingers are spaced as close together as possible to improve the guiding performance of the conical array, and minimize the likelihood of the uphole end of the fish passing between two guide fingers.
When the fingers are expanded, further lowering of the tool causes the conical array of expanded guide fingers to guide the uphole end of the fish and the latch mechanism into engagement with each other. More specifically, the combined inner surfaces of the guide fingers form a substantially conical guide cage for guiding the fish and the latch mechanism into engagement with each other. This may involve guiding the downhole end of the fishing tool toward the location of the uphole end of the fish, or vice versa, or a combination of both. After engagement of the fish with the latch mechanism, the fishing tool may be pulled uphole, retrieving the fish. During retrieval, hydraulic pressure on the piston may be reduced, allowing the fingers to be retracted to some extent by a return spring shifting the sleeve relative to the mandrel, depending upon the type of latch mechanism used and upon the type of fish.